Hi,
I think the problem is in FROM clause.
You may need to name this data group as tPersonPerformanceHist or some temp name and use the temp name in the query.
(SELECT tPersonPerformanceHist.PerformanceRatingCode FROM tPersonPerformanceHist
WHERE (tPersonPerformanceHist.PersonPerformanceEndDate =
(SELECT MAX(PersonPerformanceEndDate)FROM tPersonPerformanceHist)))